Intangible Assets and Liabilities - Components of intangible assets and liabilities (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Schedule of finite lived intangible assets and liabilities
Intangible assets and liabilities, gross	$ 149.5	$ 98.1
Intangible assets and liabilities, accumulated amortization	80.3	32.4
Assets and liabilities, weighted avg. life (years)	14 years 9 months 6 days
Below-market lease intangibles [Member] | Other liabilities [Member]
Schedule of finite lived intangible assets and liabilities
Liabilities gross balance	(8.9)	(6.8)
Liabilities accumulated amortization	(4.1)	(1.9)
Liabilities, weighted avg. life (years)	13 years 6 months 0 days
Goodwill [Member] | Other assets [Member]
Schedule of finite lived intangible assets and liabilities
Assets gross balance	3.5	3.5
Assets accumulated amortization	0	0
Deferred financing costs [Member] | Other assets [Member]
Schedule of finite lived intangible assets and liabilities
Assets gross balance	16.4	17.6
Assets accumulated amortization	4.7	7.0
Assets, weighted avg. life (years)	5 years 0 months 0 days
Above-market lease intangibles [Member] | Other assets [Member]
Schedule of finite lived intangible assets and liabilities
Assets gross balance	17.3	14.8
Assets accumulated amortization	2.9	2.1
Assets, weighted avg. life (years)	48 years 4 months 8 days
Customer relationship intangibles [Member] | Other assets [Member]
Schedule of finite lived intangible assets and liabilities
Assets gross balance	2.6	2.6
Assets accumulated amortization	0.6	0.6
Assets, weighted avg. life (years)	29 years 7 months 2 days
At Market Lease Intangibles [Member] | Real estate properties [Member]
Schedule of finite lived intangible assets and liabilities
Assets gross balance	118.6	66.4
Assets accumulated amortization	$ 76.2	$ 24.6
Assets, weighted avg. life (years)	6 years 7 months 28 days